Routines
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915C: Draw New Column
When Jetman crosses a cell boundary, point HL at the new terrain cell and DE at the screen column that has scrolled into view.
Input
HL World X
DE Pixel step
Output
HL Pointer to the cell after the drawn one
DE Screen address one character row below the column
Draw the new terrain column that has scrolled into view.
DrawNewColumn 915C LD A,E Jump to LocateTerrainCell if Jetman is moving left.
915D AND A
915E JP M,LocateTerrainCell
9161 LD DE,$0080 Add 80 to the world X.
9164 ADD HL,DE
9165 LD A,H Fetch the high byte.
9166 AND %00011111 Keep only bits 0-4.
9168 LD H,A Write it back to H.
9169 LD DE,$7000 DE=TerrainData_Active.
916C SRA H Divide the world position by 08.
916E RR L
9170 SRA H
9172 RR L
9174 SRA H
9176 RR L
9178 ADD HL,DE HL+=DE.
9179 LD DE,$50DF DE=50DF.
Continue on to DrawTerrainColumn.
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